1. Field of the Invention
The present invention relates to a method of determining a retreat permission position of a carrier arm after the delivery of a thin plate substrate (hereinafter, simply referred to as a substrate) such as, for example, a semiconductor wafer and a glass substrate for liquid crystal to a plurality of supporting pins when the substrate is to be delivered to a mounting table in a processing unit or the like via the supporting pins from the carrier arm and to a device for teaching the retreat permission position.
2. Description of the Related Art
In semiconductor wafer fabricating steps, a photolithography technique is generally used for forming a resist pattern over a surface of a substrate such as a semiconductor wafer and an LCD substrate. This photolithography technique includes a resist coating step of coating the surface of the substrate with a resist solution, an exposure processing step of exposing a circuit pattern on the formed resist film, and a developing treatment step of supplying a developing solution to the substrate after the exposure processing.
Between the above steps, various kinds of heat processing are carried out, such as, heat processing (prebake), which is carried out, for example, between the resist coating step and the exposure processing step, for improving adhesiveness between the substrate and the resist film by evaporating a residual solvent in the resist film, heat processing (post-exposure bake (PEB)), which is carried out between the exposure processing step and the developing treatment step, for preventing the occurrence of fringe or inducing an acid catalyst reaction in a chemically amplified resist (CAR), and, heat processing (post-bake), which is carried out after the developing treatment step, for removing a residual solvent in the resist and a rinse agent taken into the resist during the developing to remedy infiltration at the time of wet etching.
As a heat processing unit for use in the heat processing, a unit as shown in FIG. 8 and FIG. 9 has been conventionally used. This unit has a mounting table 25 provided with a heater 26 and capable of heating a semiconductor wafer W (hereinafter, referred to as a wafer W) as a substrate to be processed up to a predetermined temperature, proximity pins 70 for supporting the wafer W with a slight spaced interval being kept from the mounting table 25 at the time of the heat processing, and a plurality of, for example, three ascendable/descendible supporting pins 80 passing through supporting pin guiding through holes arranged in and concentrically with the mounting table 25 at a plurality of, for example, three positions at equal spaced intervals. The wafer W is supported by tips of the supporting pins 80, and the descent of the supporting pins 80 causes the wafer W to be placed on the mounting table 25, more precisely, on the proximity pins 70.
The wafer W is delivered to this heat processing unit in such a manner that a carrier arm 28 of a substrate transfer mechanism 21 holds a peripheral portion of the substrate to be processed (wafer W) to carry this wafer W to a position above the mounting table 25, and then either the carrier arm 28 is descended or the supporting pins 80 are ascended to place the wafer W on the supporting pins 80, and thereafter, the supporting pins 80 descend to place the wafer W on the mounting table 25 after the carrier arm 28 moves back to retreat outside the mounting table 25.
In such delivery, it is necessary to prevent the carrier arm 28 from obstructing the delivery step of the wafer W based on a height position at the time when the tips of, for example, three supporting pins 80 abut against a lower surface of the wafer W, namely, a position at which the supporting pins 80 support the wafer W. This means that it is necessary that appropriate determination has been made in advance on a retreat permission position from which the carrier arm 28 is to start retreating outside the mounting table 25 after delivering the wafer W to the supporting pins 80. When this position is not appropriate, the following problem occurs. For example, in the case when the carrier arm 28 is lowered to deliver the wafer W to the supporting pins 80, a lower limit position of the descent of the carrier arm 28, in other words, the timing of returning the carrier arm 28 becomes inappropriate so that the carrier arm 28 is returned with the wafer W being left placed thereon. In the case when the supporting pins 80 is hoisted to deliver the wafer W onto the supporting pins 80, an upper limit position of the ascent of the supporting pins 80, in other words, the timing of returning the carrier arm 28 becomes inappropriate so that the carrier arm 28 is returned with the wafer W being left placed thereon.
Further, in such delivery of the substrate, position adjustment of the carrier arm 28 in a horizontal plane is also important in order to prevent position deviation of the wafer W when the wafer W is delivered to the supporting pins 80.
For this purpose, an operation of teaching the carrier arm of a substrate carrier the retreat permission position of the carrier arm and a substrate delivery position (transfer teaching) has been conventionally performed by an operator prior to the actual transfer of the wafer W. Specifically, a position apart from a height position at which the tips of the aforesaid three supporting pins 80 abut against the lower surface of the wafer W, by a predetermined amount in a height direction (namely, the retreat permission position of the carrier arm) has been conventionally calculated based on operator""s gauge measurement, an operation amount of a robot arm of the substrate carrier is determined based on the retreat permission position of the carrier arm, and an arm operation is taught through manual input.
However, the operation of determining the retreat permission position of the carrier arm by the gauge measurement is difficult for the operator and also involves a safety problem. Therefore, the provision of a means for automatically determining and teaching the carrier arm the retreat permission position and so on of the carrier arm is expected.
Further, for this kind of substrate carrier provided with the aforesaid carrier arm, also expected is the provision of a method capable of teaching the carrier arm the adjustment of the extent of carrier arm forward movement in a depth direction in the horizontal plane and the fine adjustment in a right-left direction for the purpose of determining the position of the substrate, which is to be delivered to the supporting pins, in the horizontal plane.
It is an object of this invention to provide a technique of automatically determining and teaching the carrier arm the retreat permission position of the carrier arm after delivering the substrate to the supporting pins and further to provide a technique of facilitating the judgment of the substrate delivery position of the carrier arm.
A method of the present invention is a method of determining a retreat permission position of a carrier arm when the carrier arm is moved back to retreat outside a mounting table after the carrier arm carries a substrate to a position above the mounting table while holding a peripheral portion of the substrate, to thereby place the substrate on a plurality of ascendable/descendible supporting pins passing through the mounting table, the method comprising the following. Namely, preparing a disk substantially equal in size to the substrate; and providing the disk with a sensor capable of detecting whether the supporting pin exists or not, for at least one insertion hole among a plurality of insertion holes formed to allow the plural supporting pins to be inserted therethrough. Further, carrying the disk to the position above the mounting table while holding the peripheral portion of the disk by the carrier arm, and relatively moving the carrier arm and the supporting pins in a vertical direction to detect a tip of the supporting pin by the sensor; and calculating a position to which the carrier arm is to be moved in a height direction relatively to the disk from a detection position of the tip of the supporting pin, an amount of this movement exceeding at least a thickness of the carrier arm, thereby determining this position as the retreat permission position of the carrier arm.
A device of the present invention is a device for teaching a retreat permission position of a carrier arm when the carrier arm is moved back to retreat outside a mounting table after the carrier arm carries a substrate to a position above the mounting table while holding a peripheral portion of the substrate, to thereby place the substrate on a plurality of ascendable/descendible supporting pins passing through the mounting table, the device comprising: a disk substantially equal in size to the substrate, having insertion holes which allow the supporting pins to be inserted therethrough and being supportable by the carrier arm; and a sensor, which is provided on the disk, capable of detecting whether the supporting pin inserted through the insertion hole of this disk exists or not; and a controller for calculating by an operation, after receiving an output signal from the sensor, a position to which the carrier arm is to be moved in a vertical direction relatively to the disk from a detection position of a tip of the supporting pin, an amount of this movement exceeding at least a thickness of the carrier arm and for teaching this position to the carrier arm as the retreat permission position of the carrier arm.
According to the present invention, since the tip of the supporting pin is detected in the through hole by the sensor, it is possible to calculate by, for example, the operation or the like the position to which the carrier arm is to be moved relatively to the disk in the height direction from the detection position of the tip of the supporting pin, the amount of this movement exceeding at least the thickness of the carrier arm, and to automatically teach the retreat permission position of the carrier arm by using the calculated position as the retreat permission position of the carrier arm.
Further, when a disk having a through hole formed in a center portion thereof and a camera visually recognizing a known center target thereunder from the through hole is used as the aforesaid disk, the camera attached to the disk visually recognizes the known target thereunder from the through hole so that the fine adjustment of a forward movement position and a right-left position of the carrier arm can be made easily while looking at an image, thereby enabling accurate detection of a substrate delivery position.
FIG. 1 is a schematic perspective view showing an example of a teaching device according to this invention;
FIG. 2(a) and FIG. 2(b) are schematic cross sectional views of disks and a carrier arm used in this invention, FIG. 2(a) showing a state before supporting pins are inserted through insertion holes of the disks and FIG. 2(b) showing a state when the supporting pins are inserted through the insertion holes of the disks;
FIG. 3(a) and FIG. 3(b) are schematic cross sectional views of a wafer and the carrier arm in a method of this invention, FIG. 3(a) showing a state when the carrier arm descends relatively by a thickness amount of the carrier arm after the carrier arm has placed the wafer on the supporting pins, and FIG. 3(b) showing a state when the carrier arm descends relatively by an amount equal to the sum of the thickness of the carrier arm and a margin width after the carrier arm has placed the wafer on the supporting pins;
FIG. 4 is a schematic plan view of a resist solution coating and developing system to which the teaching device of this invention is applied;
FIG. 5 is a schematic front view of the resist solution coating and developing system in FIG. 4;
FIG. 6 is a schematic rear view of the resist solution coating and developing system in FIG. 4;
FIG. 7 is a schematic cross sectional view showing the structure of a heat processing unit to which the teaching device of this invention is applied;
FIG. 8 is a schematic plan view showing the structure of a carrier of the heat processing unit in FIG. 7; and
FIG. 9 is a schematic cross sectional view showing the structure of the carrier of the heat processing unit in FIG. 7.